New quantum computer simulations show improved memory use by 25pc

9 Jul 2021

Image: © agsandrew/

New software techniques could reduce research costs by streamlining simulations for solar cells, batteries and other materials.

One of the building blocks for quantum computer simulation has been refined in a new paper published in Physical Review B.

The authors are a team from Phasecraft, a spin-out of University College London (UCL) and University of Bristol hoping to refine techniques on quantum computer systems.

While quantum computers are still taking off, demonstrations are beginning to show some of their advantages.

Focusing on the quantum theory and software to improve on existing computers, the Phasecraft team states that currently intractable problems will be solved with the right mix of hardware and software.

It isn’t necessarily a case of better or worse than old systems, but optimising what the current systems can be used for. Simulating fermions is one such use.

Fermions are a type of subatomic particle defined by their spin, which has an odd half-integral angular momentum (behaviour predicted by Fermi-Direc statistics, hence their name). Elementary particles such as electrons can be fermions, as can composite particles such as protons.

“Many important fields such as chemistry and materials science are concerned with the dynamics of fermion particles in physical systems,” explained Charles Derby, a Phasecraft team member and PhD candidate at UCL.

However, modelling large systems of fermions is difficult for classical computers and much more suited to quantum systems.

A central feature of quantum computing is that, unlike a classical computer that uses binary bits, which can be either one or zero, a quantum computer uses quantum bits, or qubits, which can be one, zero or both at the same time.

“One of the most exciting potential applications for quantum computing is simulating physical systems like materials,” said Phasecraft’s Joel Klassen, who co-led the study.

“Using new tools, like quantum computers, to develop a better understanding of how the natural world works has historically often led to dramatic technological breakthroughs. Our results reduce the resources required to perform these simulations, bringing this application closer to reality.”

According to the study, Phasecraft’s computer representation of fermions outperformed previous quantum versions in memory use and algorithm size by at least 25pc.

While quantum hardware is becoming increasingly widespread, the Phasecraft team highlighted the limitations of existing devices, creating a gap between the resources software needs and what the hardware can actually achieve. This work from Phasecraft aims to close that computation gap.

Existing quantum hardware is also prone to a build-up of errors. To address this, the researchers built in an error detection system that can pick up mistakes in their computation as they go along.

From here, Phasecraft will be conducting small-scale experiments to demonstrate these resource improvements and error mitigation methods on quantum hardware. They will also work with established industry partners to explore applications in battery material simulation.

“Fermions are notoriously difficult to simulate on regular computers so being able to simulate them efficiently on a quantum device would provide a faster path to tackling hard problems in these areas of research such as understanding high temperature superconductivity or improving chemical reaction efficiency,” said Derby.

Sam Cox was a journalist at Silicon Republic covering sci-tech news